DESCRIPTION (Applicant's Abstract): Project uses the data available from the Wisconsin Maternity Leave and Health Project (WMLHP) to investigate the developmental trajectories of children's affective style and its consequences, from infancy and the preschool years through the crucial transition to school and into middle childhood. Hypothesis to be tested are: (a) affective style develops as a function of individual, affective environment, and contextual factors; and (b) affective style plays a central role in children's vulnerability and adaptability to stressors, including chronic and acute stressors as well as the normal developmental challenges of childhood. The WMLHP longitudinal data base includes data from children and families followed from pregnancy to (currently) age 5. In addition, to multiple assessments (multi method; multi reporters) of parent and child affect, stress, and child behavior (both normal and pathological), key variables most relevant to the center are measures of the emotion-potentiated startle reflex (in children) and salivary cortisol (in children, siblings, and parents; N=480), taken when the children were 4 years old. The Center will support three related activities. First, the existing data base will be used to carry out analyses focused on understanding the effects of early individual difference factors, family context/stress, and the affective environment on the development of the children's affective style as indexed by behavioral and psychobiological measures during the preschool years. Second, intensive home assessments during the second and third years of the Center will be carried out as the children are entering third grade. Here we will investigate the consequences of their affective style for adjustment to school and their socio-emotional and behavioral adjustment during this period. We will also address the question of the stability of individual differences in affective style over time, and consider if there are "critical" factors (such as family stress) that contribute to stability or instability. Finally, a subsample of children will be selected on the basis of individual and family risk factors and studied in the Center neurophysiological laboratory. Here the question is: do children at higher risk for internalizing difficulties during the transition to school also exhibit patterns of physiological vulnerability such as higher right brain activation, slower affective recovery, or tonically elevated cortisol?